Edgedetection using wavelet transform and neural networks

The method exposed in this paper represents a new edge-detection tool of a grey-level image by the cooperation of two technics : wavelet decomposition and neural networks . The first part recalls the necessary background on mono and bidimensional wavelet decomposition and their main properties . The difficult phase of the algorithm lies in the optimal recomposition of différent resolutions, in the aim to obtain thin and noiseless edges . This work is given to a neural network which constitutes the object of the second part. The main interest of this new method is to give good resuits with images whose caracteristics are completly différent, without to modify any parameters .La méthode présentée dans cet article, constitue un nouvel outil d'extraction des contours d'une image en niveaux de gris, par coopération de techniques: décomposition en ondelettes et réseaux neuromimétiques. La première partie est consacrée aux rappels nécessaires quant au formalisme de la décomposition en ondelettes, ainsi que ses principales propriétés. La phase délicate de l'algorithme réside dans la recomposition optimale des différentes résolutions, afin d'obtenir des contours fins et sans bruit. Cette tâche est avantageusement confiée à un réseau de neurones, objet de la deuxième parti

Integrate and Fire Neural Networks, Piecewise Contractive Maps and Limit Cycles

We study the global dynamics of integrate and fire neural networks composed of an arbitrary number of identical neurons interacting by inhibition and excitation. We prove that if the interactions are strong enough, then the support of the stable asymptotic dynamics consists of limit cycles. We also find sufficient conditions for the synchronization of networks containing excitatory neurons. The proofs are based on the analysis of the equivalent dynamics of a piecewise continuous Poincar\'e map associated to the system. We show that for strong interactions the Poincar\'e map is piecewise contractive. Using this contraction property, we prove that there exist a countable number of limit cycles attracting all the orbits dropping into the stable subset of the phase space. This result applies not only to the Poincar\'e map under study, but also to a wide class of general n-dimensional piecewise contractive maps.Comment: 46 pages. In this version we added many comments suggested by the referees all along the paper, we changed the introduction and the section containing the conclusions. The final version will appear in Journal of Mathematical Biology of SPRINGER and will be available at http://www.springerlink.com/content/0303-681

The Epl1 and Sm1 proteins from Trichoderma atroviride and Trichoderma virens differentially modulate systemic disease resistance against different life style pathogens in Solanum lycopersicum

"Fungi belonging to the genus Trichoderma, commonly found in soil or colonizing plant roots, exert beneficial effects on plants, including the promotion of growth and the induction of resistance to disease. T virens and T atroviride secrete the proteins Sm1 and Epl1, respectively, which elicit local and systemic disease resistance in plants. In this work, we show that these fungi promote growth in tomato (Solanum lycopersicum) plants. T virens was more effective than T atroviride in promoting biomass gain, and both fungi were capable of inducing systemic protection in tomato against Altemaria solani, Botrytis cinerea, and Pseudomonas syringae pv. tomato (Pst DC3000). Deletion (KO) of epl1 in T atroviride resulted in diminished systemic protection against A. solani and B. cinerea, whereas the T virens sm1 KO strain was less effective in protecting tomato against Pst DC3000 and B. cinerea. Importantly, overexpression (OE) of epl1 and sm1 led to an increase in disease resistance against all tested pathogens. Although the Trichoderma WT strains induced both systemic acquired resistance (SAR)-and induced systemic resistance (ISR)-related genes in tomato, inoculation of plants with OE and KO strains revealed that Epl1 and Sm1 play a minor role in the induction of these genes. However, we found that Epl1 and Sm I induce the expression of a peroxidase and an alpha-dioxygenase encoding genes, respectively, which could be important for tomato protection by Trichoderma spp. Altogether, these observations indicate that colonization by beneficial and or infection by pathogenic microorganisms dictates many of the outcomes in plants, which are more complex than previously thought.

A Nuclear Localization of the Infectious Haematopoietic Necrosis Virus NV Protein Is Necessary for Optimal Viral Growth

The nonvirion (NV) protein of infectious hematopoietic necrosis virus (IHNV) has been previously reported to be essential for efficient growth and pathogenicity of IHNV. However, little is known about the mechanism by which the NV supports the viral growth. In this study, cellular localization of NV and its role in IHNV growth in host cells was investigated. Through transient transfection in RTG-2 cells of NV fused to green fluorescent protein (GFP), a nuclear localization of NV was demonstrated. Deletion analyses showed that the 32EGDL35 residues were essential for nuclear localization of NV protein, and fusion of these 4 amino acids to GFP directed its transport to the nucleus. We generated a recombinant IHNV, rIHNV-NV-ΔEGDL in which the 32EGDL35 was deleted from the NV. rIHNVs with wild-type NV (rIHNV-NV) or with the NV gene replaced with GFP (rIHNV-ΔNV-GFP) were used as controls. RTG-2 cells infected with rIHNV-ΔNV-GFP and rIHNV-NV-ΔEGDL yielded 12- and 5-fold less infectious virion, respectively, than wild type rIHNV-infected cells at 48 h post-infection (p.i.). While treatment with poly I∶C at 24 h p.i. did not inhibit replication of wild-type rIHNVs, replication rates of rIHNV-ΔNV-GFP and rIHNV-NV-ΔEGDL were inhibited by poly I∶C. In addition, both rIHNV-ΔNV and rIHNV-NV-ΔEGDL induced higher levels of expressions of both IFN1 and Mx1 than wild-type rIHNV. These data suggest that the IHNV NV may support the growth of IHNV through inhibition of the INF system and the amino acid residues of 32EGDL35 responsible for nuclear localization are important for the inhibitory activity of NV

Contribution of neural network to an edge-detection tool using wavelets transformation

The method exposed in this paper represents a new edge-detection tool of a greylevel image by the cooperation of two technics : wavelet decomposition and neural networks. The first part recalls the necessary background on mono and bidimensional wavelet decomposition and their main properties. The difficult phase of the algorithm lies in the optimal recomposition of different resolutions, in the aim to obtain thin and noiseless edges. This work is given to a neural network which constitutes the object of the second part The main interest of this new method is to give good results with images whose caracteristics are completly different, without to modify any parametersLa méthode présentée dans cet article, constitue un nouvel outil d'extraction des contours d'une image en niveaux de gris, par coopération de techniques : décomposition en ondelettes et réseaux neuromimétiques. La première partie est consacrée aux rappels nécessaires quant au formalisme de la décomposition en ondelettes, ainsi que ses principales propriétés. La phase délicate de l'algorithme réside dans la recomposition optimale des différentes résolutions, afin d'obtenir des contours fins et sans bruit. Cette tâche est avantageusement confiée à un réseau de neurones, objet de la deuxième partie. L'attrait majeur de cette nouvelle technique, est sa capacité à traiter correctement des images aux caractéristiques très différentes, sans avoir à modifier de paramètre

ARCHITECTURAL MODELISATION OF THE BIOLOGICAL VISUAL SYSTEM FOR THE IMAGE SEGMENTATION

This article deals with the research of the contours by the modélisation of the biological visual systems. The segmentation tool presented in this article takes advantage of orientation selection mechanisms which appear in the visual cortex, so that fine well situated edges are obtained in a grey scale image. The search for the best spatial resolution limits our study to the central part of the fovea. On this basis, we present also a method of research of angular points in the image of the oriented contours available in the cortical columnsCet article est consacré à la recherche de contours par la modélisation des systèmes visuels biologiques. L'outil de segmentation présenté, tire profit des mécanismes de sélectivité à l'orientation présents dans le cortex visuel, pour obtenir des contours fins et bien localisés dans une image en niveaux de gris. La recherche de la meilleure résolution spatiale limite notre étude à la partie centrale de la fovéa. Sur cette base, nous présentons également une méthode de recherche de points anguleux dans l'image des contours orientés disponibles au sein des colonnes corticale